1. Field of the Invention
The invention relates to a method and a device for producing a printing image carrier on prefabricated carrier material in a printing machine.
The published German Patent Document DE 195 3 6 884 C1 describes a device for wrapping a flexible printing image carrier around a printing form cylinder. Provided in the interior of the printing form cylinder is a first winding spool or coil for unwinding a printing image carrier which is drawable onto the casing or jacket surface of the printing form cylinder, and a second winding coil or spool for winding the printing image carrier drawn onto the jacket surface. Formed in the circumferential surface of the printing form cylinder is a single opening to an indentation in the interior of the printing form cylinder, wherein the first and the second winding spools or coils are arranged together. From this opening, the printing image carrier can be wound from the first winding coil or spool onto the jacket surface, and from the jacket surface onto the second winding coil or spool.
This heretofore known device of the German patent document is further characterized by the feature of a bearing part which is disposed so as to be removable from the interior of the printing form cylinder in the state wherein it is installed in the printing machine.
The European Patent Document EP 0 770 494 A2 is concerned with a method for making a printing form, the method being performed within a printing machine. An image-wise exposure of an image element takes place on a hydrophilic surface of a printing plate of an image-carrying layer. Contained in the image-carrying layer are hydrophilic thermoplastic polymer particles, which are dispersed in a hydrophobic binder. Furthermore, a mixture is provided which converts light into heat, the image element created in this way being applied to an impression cylinder which is provided in a rotary printing machine, and is inked via a dampening solution and/or ink during the rotation of the impression cylinder.
The published European Patent Document EP 0 802 457 A1 describes a device for producing and producing an image on a printing plate. A print carrier is disclosed, and equipment is provided for applying a uniform coating; devices are also provided for exposing the uniform coating in accordance with an image pattern, and further devices are provided for developing the uniform coating so that an image remains on the print carrier.
The printing image includes ink-accepting or ink-friendly areas on an ink-repellent background, or ink-repellent areas on an ink-accepting or ink-friendly background. The print carrier includes a cylinder, on the circumferential surface of which an element in sheet or plate form is mounted, the surface of the element being either an ink-accepting or ink-repellent type of surface. The aforementioned published European Patent Document EP 0 802 457 A1 also discloses a method for making a print carrier, the device described hereinabove being used therefor, as well as a coating fluid to be used in the device.
U.S. Pat. No. 5,713,287 discloses an imaging or image-generating method wherein the surface of a single-layer coating is modified.
In a direct imaging system with a gapless cylinder, the latter is provided in the printing machine with a radiation-curable polymer. After curing the polymer, the surface of the polymer is modified by selective irradiation with a laser light source, so that the affinity to the printing ink is changed. The cylinder thus formed is installed, in the place of a plate cylinder, in an offset printing machine, which operates either conventionally or without water. Because only the surface of the cylinder is selectively modified by the laser, the coating thickness and uniformity are of little concern. After the printing operation, the cylinder is cleaned, for which a cleaning station similar to a blanket washer in printing machines is installed. The cleaning operation does not have to be complete, because the surface of the cylinder of the printing unit is never entirely exposed to the printing ink. The proposed system is compatible with existing rotary printing-machine arrangements, because it can be accommodated in the area in the printing units presently provided for plate changing in the printing machines.
In the construction disclosed in the aforementioned U.S. Pat. No. 5,713,287, after the printing job has been completed, the polymer coating which is able to be influenced must be removed again, at least for the most part, from the surface of the print carrier, before a new neutral coating, i.e., a coating not yet irradiated by a laser light source, is applied as a precondition for a printing image to be newly generated by forming an image on the printing form in the printing machine for the next printing job. Even if the polymer coating is not completely removed from the surface of the printing form cylinder after the preceding printing job has been completed, the adhesion of the polymer to be newly applied for the next printing job must be so good that the polymer coating for the following job has the same high residence time on the printing form with repeated reproducibility.
It has been found that the adhesion between the contact surface of the carrier material to which the polymer coating to be influenced is applied, as well as the polymer material to be influenced, in repeated application of the treatable polymer material, is inadequate for achieving the same high and consequently adequate residence time of the print carrier as is the case when the treatable polymer is applied for the first time.
Attempts have been made to improve the inadequate adhesion between the contact surface of the carrier material and the treatable polymer by improving the composition, i.e., the formulation, of the treatable polymer. Furthermore, attempts have been made to improve the adhesion between the contact surfaces by optimizing the cleaning process and the cleaning agents provided therefor. Attempts have also been made to increase the adhesion of the polymer by selecting different carrier materials and the nature of the surface thereof and the surface roughness thereof, respectively. Furthermore, parameters specific to the printing machine, such as, for example, the pressing together of mutually cooperating roller surfaces, and inks of differing viscosity have been used.
It is accordingly an object of the invention to provide a method and a device for producing a printing image carrier in prefabricated carrier material in a printing machine with which it is possible to provide economically a polymer coating that can be influenced for the printing and can be disposed of readily after the printing.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for producing a print carrier within a printing machine, which comprises providing on a cylinder of the printing machine a prefabricated carrier material having a contact surface, and, within the printing machine, applying an impressionable or influenceable polymer to the contact surface of the prefabricated carrier material.
In accordance with another mode, the method of the invention includes prefabricating the carrier material in roll form on winding spools.
In accordance with a further mode, the method of the invention includes prefabricating the carrier material as an exchangeable sleeve, with the contact surface thereof receiving thereon the impressionable or influenceable polymer coating.
In accordance with an added mode, the method of the invention includes prefabricating the carrier material by pre-cutting it into sheet form, and preparing the contact surface thereof for adhesion with the impressionable polymer coating.
In accordance with an additional mode, the method of the invention includes removing the carrier material pre-cut into sheet form from a jacket surface of the cylinder and applying the carrier material to the jacket surface, respectively, by an automatic changing system.
In accordance with yet another mode, the method of the invention includes one of spraying the impressionable polymer and transferring the impressionable polymer from another medium, respectively, onto the carrier material, which has been suitably prepared, for effecting the adhesion thereof.
In accordance with yet a further mode, the method of the invention includes applying the impressionable polymer by contact application with an entrained surface of one of a rotational body and a band-shaped element, respectively.
In accordance with yet an added mode, the method of the invention includes fixing the impressionable polymer coating on the carrier material by irradiating the applied impressionable polymer coating.
In accordance with yet an additional mode, the method of the invention includes fixing the impressionable polymer coating by pre-heating the carrier material.
In accordance with still another mode, the method of the invention includes providing the carrier material in film form and of dimensionally stable polyester.
In accordance with still a further mode, the method of the invention includes providing the carrier material in a rounded form in the winding direction, and disposing the carrier material in a cavity formed in the printing form cylinder.
In accordance with still an added mode, the method of the invention includes, during an imaging and a printing process, bonding the carrier material by at least one of suction and magnetic cohesion to a jacket surface of the printing form cylinder.
In accordance with still an additional mode, the method of the invention includes, after completing a printing job, winding the carrier material on a jacket surface of the cylinder, unwinding a used portion of the carrier material from the jacket surface, and winding a portion of the carrier material to be provided with new polymer coating onto the jacket surface.
In accordance with another mode, the method of the invention includes forming the carrier material of polyester material that has been chemically and physically prepared for an application of the polymer coating and a fixing thereof on the surface of the carrier material.
In accordance with a further mode, the method of the invention includes applying and fixing the impressionable polymer simultaneously in all printing units of a printing machine.
In accordance with an added mode, the method of the invention includes reprocessing the used supply of carrier material outside the printing machine.
In accordance with an additional mode, the method of the invention includes performing an additional step of fixing the impressionable polymer coating applied to the carrier material which has been suitably prepared.
In accordance with yet another mode, the method of the invention includes providing the prefabricated carrier material as a roll, applying the roll outside the printing form cylinder, and automatically cutting off a required length of carrier material and mounting the length of carrier material on a jacket surface of the printing form cylinder.
In accordance with yet a further mode, the method of the invention includes providing a suitable roughness for producing a frictional connection between a jacket surface and an underside of the carrier material to be applied.
In accordance with yet an added mode, the method of the invention includes providing that the jacket surface of the printing form cylinder receiving the carrier material is porous.
In accordance with yet an additional mode, the method of the invention includes, following the end of the printing job, at least one of winding further and removing, respectively, the carrier material which can receive the impressionable polymer coating.
In accordance with another aspect of the invention, there is provided a printing machine having an impression cylinder, comprising a device for applying a prefabricated carrier material to the surface of the impression cylinder, and a device for applying an impressionable polymer to a contact surface of the prefabricated carrier material.
In accordance with a concomitant feature of the invention, the device for applying the prefabricated carrier material has winding spools.
The advantages of the method proposed according to the invention are to be seen in particular in that the influenceable or impressionable polymer coating on the carrier material does not have to be removed, not even partly, for the respective printing job that has been completed. This saves valuable time and dispenses with a cleaning device otherwise necessary for cleaning, which may cause disruptions in the overall performance of the process. The cleaning device otherwise to be provided also requires space, which is in any case limited and, furthermore, causes considerable production costs. According to the method preferably proposed in accordance with the invention, after completion of the respective printing job, the carrier material, which may, for example, be in the form of a film, is merely wound on, whereby the portion of the carrier material with which printing has just been performed is removed from the surface of the printing form cylinder and, for example, drawn into the interior of the printing form cylinder. At the same time, a new portion, not yet coated with the influenceable or impressionable polymer coating, is placed onto the jacket surface of the cylinder. This new portion is coated with an influenceable polymer either during the wind-up onto the jacket surface or after the winding and tensioning of the carrier material. This is followed by fixing the influenceable polymer coating in the printing machine, so that the printing machine is made-ready or prepared for the next printing job to be performed.
According to another advantageous implementational mode of the method of the invention, the carrier material is prefabricated in roll form on winding spools. This offers the advantage that the surface coming into contact with the influenceable polymer does not come into contact for a prolonged period with either light or oxygen, and consequently is well protected against oxidation and light. In addition, it is quite possible for the surface of the carrier material also to be prepared at low cost outside the printing machine in clean-room or under vacuum conditions.
In an alternative mode of the method proposed according to the invention, the carrier material can be prefabricated as a quickly exchangeable sleeve with a jacket or lateral surface receiving the influenceable polymer. The quickly exchangeable sleeve could be reprocessed offline or, if it is appropriately inexpensive, disposed of directly after completion of the printing job. The components of the sleeve-shaped carrier material may be produced, for example, from steel, aluminum, glass-fiber reinforced plastic material or suitable polyester material.
Furthermore, there is the possibility of using the method proposed according to the invention for storing the prefabricated carrier material in a spool device or some other suitable transporting device outside the printing machine and applying it as and when required to the surface of the printing form cylinder to be provided with the carrier material, detaching a corresponding portion of the prefabricated carrier material from this transporting device and applying it to the surface of the printing form cylinder to be provided therewith.
According to a further mode of the method proposed according to the invention, the prefabrication of the carrier material is possible as a pre-cut carrier material in sheet form. With such a fabricated carrier material, one surface is provided for the adhesion of the influenceable polymer coating, it being possible to use semi-automatic or fully automatic plate feeding systems of a known construction for applying such planar carrier material portions similar to printing plates.
The application of the impressionable or influenceable polymer coating to the surface of the carrier material prepared for the adhesion of the polymer coating may be effected by spraying with an appropriate spraying device or by material transfer from another medium. Apart from applying impressionable polymer in coating form by spraying it on or by material transfer from another medium, application of the impressionable polymer may also take place by contact with a concurrently moved or entrained surface. A concurrently moved or entrained surface may be, for example, the jacket surface of an application roller, or the upper side of an element in band form, which applies the polymer material and is driven externally or by the printing machine itself.
After the polymer coating has been applied in the manner proposed, in accordance with the invention, to the upper side of the carrier material suitable for the adhesion of the polymer coating, the application of the polymer coating takes place on the upper side of the carrier material on the cylinder, for example, the printing form cylinder of a rotary printing machine. The fixing of the influenceable polymer coating on the carrier material may take place on the one hand by irradiating the applied, influenceable polymer coating on the cylinder. For this purpose, a radiation source may be provided, which can be operated with different intensities over the width of the cylinder respectively receiving the carrier material, which also applies in an analogous way to the intensity control of the radiation source in the circumferential direction of the carrier material surface to be irradiated. Besides irradiating the freshly applied polymer coating on the carrier material on the lateral or jacket surface of a printing form cylinder, fixing of the influenceable polymer coating is also possible by pre-heating the carrier material. For pre-heating the carrier material, it is possible, for example, for the winding spools receiving the supply of carrier material and accommodated in the cavity of the cylinder to be traversed by heating medium, for example, temperature-controlled water, and for pre-heating the wound-up supply of carrier material.
The carrier material may be in sheet form on the winding spools, which are exchangeably fitted into the cavity of a printing form cylinder of a rotary printing press, and comprise dimensionally stable polyester material.
To ensure reproducibility and quality assurance, slippage of the carrier material provided with an influenceable polymer coating can be prevented during the imaging or printing process by suction and/or magnetic cohesion on the lateral surface of the printing form cylinder. According to the method proposed in accordance with the invention, after completion of the printing job, the carrier material, which is preferably stored in spool form in the interior of the printing form cylinder, can be wound on on the lateral surface of the cylinder, the used portion of the carrier material with the polymer coating taken up thereon being unwound from the jacket or lateral surface, and it being possible for a portion of the carrier material to be provided with a new polymer coating within the printing machine to be newly applied to the circumferential surface of the printing form cylinder.
In a preferred embodiment, the carrier material is a polyester material, which is chemically and physically prepared for the application of the polymer coating and the fixing thereof on the surface of the carrier material.
According to the method proposed in accordance with the invention, the influenceable polymer coating can be simultaneously applied in all the printing units of a printing machine comprising a plurality of printing units and can be fixed on the respective lateral surfaces of the printing form cylinders. After the supply winding spool has been used up, i.e., the winding spool taking up the used portion of the carrier material is filled with the used supply of carrier material, reprocessing of the used carrier material and conditioning of the surface can be performed outside the rotary printing press, so that the inexpensive carrier material can be used repeatedly.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as a method and device for producing a printing image carrier on prefabricated carrier material, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: